Apparatus for making acoustic resistances



2 Shets-Sheet 1 FIG. 8

nvvs/v TOR (-l. C. HARRISON ATTORNEY H. C. HARRISON APPARATUS FOR MAKING ACOUSTIC RESISTANCES Filed March 16, 1933 Feb. 12, 1935.

T EHEQE VII/1V! 571.9554

Feb. 12, 1935. .H, c. HARRISON APPARATUS MAKING ACOUSTIC RESISTANCES Filed March 16, 1933 2 Sheets-Sheet 2 /NVENTOR H. C. HARE/SON ATTORNEY Patented Feb; 12, 1935 i 1,991,206

p 1,991,206 f f APPARATUS: FOR MAKING ACOUSTIC i RESISTANCES *Henry 0. Harrison, Port Washington, N.Y., as-

' Signor to Bell Telephone Laboratories; Incor- Y porated, New YorlgN'. Y., a corporationof. New Yorkw .f ApplicationMarcli. 16, ;,l933,fS eri a.lNo. 661,045 t g d 1o Claims."(l. 29-44)- .Thissinvention relates to acoustic material material. J'I'he openings used may be rectangutoathe apparatus by which it is made. lar slotsin which case the width of the slot deter- An object, of thisinvention thexprovision of mines the ratio of resistance to reactance of the apparatus for making a fire-proof sound absorb: damping material. and together with the ing material suitable for damping sound vibra spacing of the slots. determines the magnitudeof 5 tions in sound studios, auditoriums and like; the impedance of the material; By changing the places. width and spacingof the slots a wideyrange-of U Another object of the invention is the provision} acoustic impedancesi may be secured. I

of apparatus. for making-with a high degree of The preietred form of the acoustic damping precision'an acousticimpedance for controlling material is shownin FigsL'l'and 2. The slot 20." 1,9, I

acousticvibrati'ons. p i

In accordance with the invention a sheetof and thebars 21 formed by the material between.

metal, as for. example, zinc, aluminum,duralutheslotsare approximatelyvflfll". wide. Be-

min, brass or. any other suitable material is tween the rows of slots thereis left a solid portionmaybe approximately 0.00115" wide and 5% long 15 formed. with very narrow slots at adistance apart orlandg2 2 which maybeg fin n g such that the sheet so formed presents substanthickness oi the material andhence the depth of.

tially no reflecting surface to sound waves. V the slot is ,007. "Ifhesef dimensions are purely V In the formation of the acoustic resistance, a illustrative and; may be variedto, suit particular. thinsheet of metal is sheared into a plurality of conditions. The spacingof the Slot, that is, the

.0 verynarrow parallel bars joined at intervals by width of the bars 21;is limited, however, by that 20.

are swedged to separate the bars. i i v theinfluence of sound waves. I The acoustic resistance and the machine. by Thematerial must be, ductileflto withstand which it is made are shown in the accompanying swedgingwithout cracking. Zinc has been found drawings in which: i to bevery satisfactoryin this respect and it has 25 Fig. 1 isa planview of the acoustic resistance in addition the quality of non-infiammability withtlie slots therein greatly enlarged; whichis necessary for fireproof constructions. Fig. 2 is a front elevation of the resistance of It isapparen't that the thinness of the material. Fig. 1, sectioned through the lands; and the microscopic width of the slot preclude the unsheared portions and the unsheared portions width at which'the bars begin to vibrate under Fig. 3 is a perspective of the knives usedto shear use of ordinary perforating and shearing meth 39;

the materialy i i ods in makingthe-materialu For example, in Figs. 4 and 5 are side elevations insection of shearing thin stock withparallel knives (as must the knives and materialshowing the knives in be the 'case here), unlesscertain precautions are operative and inoperative positions, respectively; taken the material will bend instead of. shear.

Fig. 6 is. a side elevation in section of the "Ihen,,too,-it is almost impossible tofconstruct a 35 wed e; 2 i p d punch Orr-he order orloois inch by ig inchwhich 7. is thecorresponding front elevation of will last for anypractical length of time.

i I f I i Attempts havebeenmade to etch the slotsinto Fig; 8is a perspective of an alternative form the. material but suchmethods usually. require Ofknife; i considerable time and the slots made-thereby are I Fig. 9 is a perspective of the machine showing usually ragged and not uniform. p i I the material entering and leavingit; and i The present method may bedivided intotwo i Fig. 10 is a side elevation of the machinesecgeneral steps,- the first of which merely makes an tioned through the center to expose the working incisionin the material and the second squeezes partsthereofim i i p t The principle on which the design ofthesound its walls. The first step is illustrated in Figs. 4 absorbing material is based is well known andis and 5 andthe second inFigs. 6 and "7. described at length-in United'States PatentNoj. Referring to Fig. 51 theblank material is fed 1,854,830 to P.B.Fianders, filed April 28, 1928 and. from the left between the upper knife 23 and dated April 19, 1932. It will suffice for the purlowerknife .24. Theknives used are shown in poses of this invention to state that the material perspective in Fig. 3' and; comprise two hardened i must have a series of openings, the number and metal. blocks. with sharpened i edges which are magnitude of which. are such thattheviscosity divided into a series of cooperatinglcutting edges of: the air. moving therein is effective totirnp'edev by shallowslots the purpose of which is to form the progressof soundwaves'impinging uponthe the landsjznot thet finished material. Adj c n thematerial at the ends of the incisionto spread 5 each knife is a flat surface and 26. Surface 25 is a continuation of the cutting edge of the upper knife 23, but surface 26 is depressed below the cutting edge of lower knife 24. a distance which is less than the thickness of the blank material. These surfaces serve two important functions one of which is to prevent the material from bending and thus escaping shear and the other is to prevent the shear at the knife edges from being com plete. As shown in Fig. 4, the upper knife 23 is at the bottom of its stroke and the material has "at its upperend and free to move vertically in a been partly sheared.-

When the upper knife 23 is raised, the material is advanced to the right a distance'equal to the width of the bars 21 of Fig.1. The material is now deformed as shown in Fig. 5. Due to the incompleteness of the shear't he material tends to adhere to the upperknife and thus blocks any attempt to feed it through the machine. Forthis reasona strap 38 supported by a screw 39 ridin in a vertical slot in'the strap'38 ismade to bear downupon thematerial at all times by means of a resilient medium 40, such as rubber interposed between the strap 38 and the-upper knife support 41. On descending upon the material, the upper knife 23 again partly shears the new material, but the surface'25 'cooperating with surface 26 depresses the material between the previous shear and. the new shear and inldoing so completes the previous, shear and forms a distinct bar. There no separation between the bars atthis point, however, and, the material is opaque. The shear is merely an incision such as is made by a sharp blade ina blockof rubber.

The second step is to-separate the'bars and this is. done by compressing the .unsheared lands 22 beyond the elastic limit'of the material and thus producing a permanent longitudinal elongation therein which causes thebars to separate. For this purpose. a wedged shaped swedge with a blunt edge is used.

Referring to Fig. 6', 2'? is a side View of the swedge. Directly beneath the swedge 2'7 and extending considerably beyond both sides of it is an anvil 28 mounted upon a stiff springer other resilient support 29 which is set into a rigid frame 61. Secured to the swedge 27 is a flat hammer 31 which is substantially coextensive with the anvil 28. The swedge 2'7 is not inthe plane of the hammer 31 but extends slightly below it and as the swedge and hammer descend upon the material, the swedge is the first to contact the niateriah Since its area of contact is small, the total pressure exerted uponthe anvil 28 by the swedge 27 is not large enough to depress it against the force of spring 29. The swedge is consequently driven into the material and compresses it transversely but elongates it longitudinally andthe bars are separated; The swedge continuesto squeeze the material until thehammer 31engages the material, at which point the pressure increases rapidly to a predetermined limiting value greater than'the resistanceof the spring, and the anvil is depressed. When the swedge is raised'thema terial'will be found to be permanently elongated and the bars separated. I I

It is evident that'the amount of elongation depends upon the depth to which the swedge is forced into the materialand the frequency 'ofthe swedgingstroke per unit length ofmaterial. To

change the spacing of the'bars it is, therefore,

necessary to change one or bothof these factors. Inthe present apparatus it has been found more expedient to make the swedging depth the adjust-" able factor rather than-the frequency of the stroke and accordingly means are provided for changing the amount of protrusion of the swedge 2'7 below the hammer surface 31. Since the material used is very thin the adjustment of the purpose. It is incorporated into the swedge in the following manner:

The swedge is formed from a rod 32 threaded hollow bolt 33. .The bolt 33 is threaded on the outside with a coarser thread than the thread on the'rod 32 and is heldsecurely to the reciprocating frame 34 by nut 35.. The head 36 of the bolt forms the hammer 31. The rod 32 is restrained torsionally by a suitable dog arrangement such as a non-circular opening in the head 36 of the bolt 33 cooperating with a similarly shaped portion of therod'32.; A cap 37'fits over the bolt 33 and the protruding rod 32 and is threaded so as to engage the threads of both rod and bolt As the cap is turned, it moves relative to the bolt and rod but due tothe differencein the pitches of the bolt and rod threads, the rodmoves with the cap at a rate equivalent to thedifierence in the pitches of the thread. 1

Thus, each thread is made large enough to possess the requisite strength and yetthe swedge is capable of adjustment to a fraction ofa thousandthof an inch. 7

A-somewhat similar differential thread may be used to adjust the individual knives of Fig. 8.

Theblade 42 is supported in an S-shaped section i comprised of horizontal sections 43, 44 and 45 connected-together by spring hinges 46 and 4'7. Between the horizontal sections are wedges 48 and i9 cooperating with the adjacent and non-parallel used with very wide material where it is difficult to secure absolutealignment of tworigid blades such as those of Fig. 3.

For uniformity in thejfinished" product, it is necessary that the shearing, swedging and feeding operations "be in synchronism with one .an-

other. This can best be achieved by incorporating the several operations into a single machine. Such a machine is shown in Figs. 9 and 10.

Referring to Fig. 10 in which a cross-section of the machine is shown, is a rigid framesup porting. a bench 61 along which the material passes. At one'end of the bench 61 isthe lower knife 24, adjacentsurface 26, anvil 28 and supporting spring 29. Some distance removed from the knife 24 and at the opposite end of the bench 61- is a pair of feed rolls (Band 64. A reciprocating head 65 bearing the upper knife -23,.adja-- cent surface 25, hammer 31 and swedge 2'7, is

suspended over the bench 61 from a rigid iron beam 66 to'which it issecured by suitable'screws 67, and-as this comprises thesole means of support, the head 65 forms a cantilever beam. The vertical'dimension of the head at the support 58 is reduced sothat-it formsa springhinge about which the head can vibrate.

"The head -65is driven by rotating cams 69 keyed to camshaft 70 and supported in a rigid beam 71 which is secu-red to the frame GO. The cam cooperates with-roller followers 72 in the head 65. To maintain the followersin contact with the rotating cams an initial flexure is. introduced into the 1 spring hinge 68. 1 It "is often desirable to adjust the position of the head 65 relative to the lower knife 24 and to this end a second rigid beam 73 firmly secured to frame 60 is provided-with a bolt 74 holding the beam, 66 to beam '73., The adjusting is done by inserting shims 75 between beams 66 and '73. Beam 66 is secured to frame 60 by bolts 76 cooperating witha slotted opening in the beam and when the adjustment is completed these bolts are tightened.

A bracket '77 is provided to support the adjustable'lower knives of Fig. 8.

The driving means for the machine is shown in Fig. 9. An electric motor 80 or other source of power is belt connected to a pulley 81 which is keyed to cam shaft 70. The feed rolls 63 and 64 are driven from the cam shaft 70 by an eccentric 82, eccentric rod 83 and bell crank 84 cooperating frictionally with Wheel 85 which a is keyed to the shaft 91 of the lower roll 63. The

bell crank 84 is pivoted about a pin 86 secured to lever 8'7 which is free to rotate about shaft 91, and the arm in contact with the surface of wheel 85 is held against the wheel by means of a spring 88. A brake against the counter-clockwise rotation of wheel 85 is secured by means of a pivoted arm 89 and a springf90.

As thepulley 81 is rotated, cams 69 force the head 65 downward against the action of the spring hinge 68 and the shearing and swedging operations are then performed. While the knives and swedges are in contact with the material, eccetric 82 is moving the eccentric rod 83 to the left which releases the pressure of arm 86 on wheel 85. The wheel is held motionless under the ac-' tion of brake 89 and no pull is exerted. upon the material byrolls63 and 64. Whenithe cam permits the head to return to its upper position and so release the material, the eccentric 82 pushes eccentric rod 83 to the right which increases the pressure between arm 86 and wheel 85 whereupon the wheel is rotated until the eccentric rod ceases to move, at which point the pressure of the brake 89 will exceed the pressure of arm 86 and the wheel will stop. While it is moving, the rolls 63 and State advancing the material past the knives, a distance equal tothe width of a bar 21 (Fig. 1).

In addition to feeding the material through the machine the rolls 63 and 64 can be made to take the place of the swedge 27 by providing ridges (not shown) on the rolls to cooperate with the lands and thus by the application of sufficient pressure, reduce the thickness of the lands and elongate the material.

It is understood that the machine and method shown can be used with materials of greater width than that indicated in Fig. 1 and that the scope of the invention is not to be limited to the specific form illustrated, but is to be determined by the appended claims.

What is claimed is: 1. Apparatus for making an acoustic resistance of solid material comprising a pair of shear ing knives, a flat surface adjacent each knife, one of said surfaces being a continuation of the cutting edge of one of the knives and the other being removed from the, cutting edge of the second kn-ife, means ton-feeding the materialregue larl-y to the knivesyand means *forcc'ausing the knives and surfaces to move relative to one .an..-

other whereby the material is first partly sheared by the knives and on feedingsnew .material *to l the knives the; shear is completed by thepaction of the adjacent surfaces on. the material.

ZJln a deV-ice for making an acoustic resistance a shearing knife and :means for reciprocate ing said knife comprising a spring hinge supcooperating with the rollers to depress them at predetermined intervals.

3. A machine for making an acoustic resistance of sheet metal comprising a shearing knife adapted to make an incision in thematerial and a swedge adapted to, cooperate with the material to separate the walls of the incision, said swedge comprising a hammer, a protrusion on the hammer, an anvilcooperating with the hammer, a support for the anvil and spring means intermediate the anvil and anvil support yieldable only under a predetermined pressure greater than that.

between the protrusion and anvil and lessthan that between the hammer and anvil whereby the protrusion is effective to swedge the material.

4. A machine as in claim 3 and means for varying the height of the protrusion of the swedge above the surface of the hammer whereby the extension of the material can be varied.

5. A machine for making an acoustic resistance of sheet metalcomprising a pair of cooperating shears adapted. to make a plurality of incisions in the material, separated by lands, means for simultaneously swedging the lands and means cooper- 10 port for the knife, rollers in the support and cams ating with the shears and swedging means for drawingthe material through the machine at predetermined intervalsl 6. Amachine as inclaim 5 and means for re moving the material from the shears after each incision to permit it to be drawn through the machine.

7. A machine for making an acoustic resistance comprising a plurality of shears comprised, of a plurality of individual knives cooperating with portions of a common knife, means for moving I second knife, and means for moving meet the knives relative to its cooperating knife comprising a support, rollers therein, rotating cams cooperating with the rollers, driving meanstherefor and resilient means for maintaining the rollers in contact with the cam, means for swedging the material comprising a pairof parallel surfaces adapted to move relative to oneanother, a protrusion on one of the surfaces and means for limiting the pressure between the surfaces whereby the thickness of the material passing therebetween is reduced and its length increased, and means in synchronsim with the shearing and. swedging means for feeding the material into the machine, comprising a pair of rollers driven intermittently from the shaft of the rotating cam.

edge of the common,

9. Apparatus for making an incision in a thin fiat material comprising means for holding a portion of the material stationary, means for displacing the adjacent portion transversely of its surface whereby the adjacent portion-is severed from the stationary portion and means for restoring the displaced portion to the plane of the stationary portion.

10. Apparatus for making an incision in a thin flat material comprising means for holding a portion of the material stationary, means for displacing the lesser width of the adjacent portion transversely of its surface, whereby the lesser width is severed from the stationary portion and a pair of relatively movable similar surfaces adapted to bridge both portions to restore them to the same plane. a HENRY C. HARRISON. 

